1. Field of the Invention
The present invention relates to an information storage medium (or an information recording medium), an information reproduction device, and an information reproduction method.
2. Description of the Related Art
As such an information storage medium, there has been an optical disk called a digital versatile disk (DVD) capable of reproducing digital information using a focused light. Specifications of the current DVD include read-only DVD-ROM specifications, write-once DVD-R specifications, rewritable-type (about 10,000 times) DVD-RW, and rewritable-type (10,000 times or more) DVD-RAM specifications. Any specifications have format specifications which define a data structure recorded on an optical disk (information storage medium) of video information (video data, sub-picture data, and audio data, generically referred to as video objects) itself, and a data structure of management data for managing video information.
The read-only current DVD video specifications simultaneously deal with a large number of languages, and multi-scene presentation is possible such as multi-angle and multi-story. Additionally, there are varieties of menu screens, it is easy for users to directly access desired scenes, and the specifications have formats capable of providing video content which is easily used by the users (see U.S. Pat. No. 5,636,200, and Japanese Patent No. 2,677,775, for example).
As described above, the read-only current DVD video specifications have the formats capable of the video content easily usable by the users, but there has been a demand for improvements of the specifications in order that the users may further easily use the content and content representing power may be further enriched for the users.
Moreover, there is a problem that authoring (preparation and edition of programs to be recorded in the DVD video disk) is complicated in order to provide the content easy to use by the users.
Parts of the current DVD video specifications lacking in content representing power for the users, and parts difficult for the users to use or parts which are complicated in the authoring for providing the content easy to use by the users will be specifically listed.
[1] Difficult for the user to use. Alternatively, the authoring has been complicated in order to prepare the content easy to use by the users.
(A) Disadvantages with respect to a presentation start position at a time when presentation of a title is interrupted halfway to perform another processing, and the presentation of the title is restarted.
(A1) The presentation of video is interrupted, presentation is switched to menu or another video, and the presentation cannot be restarted from the interrupted position.
The presentation of a specific video title is interrupted halfway during the presentation to switch to the menu screen, bonus content is then played back halfway or to the end, and afterwards the video title interrupted halfway is to be played back. However, the content prepared by conventional DVD video specifications cannot be played back only from a start position of the video title in many cases. This is because resume information (presentation interrupted position information) of the previous specific video title is rewritten into position information of the bonus content in a stage in which the presentation of the bonus content is started. A complicated authoring process is required in order to obtain the content such that the presentation can be started from the interrupted position of the previous video title after the bonus content is played back halfway or to the end.
(A2) The presentation cannot be started from a good place to start, when a game is to be resumed after the interruption of the presentation in the game or the like.
In case of the “game” (e.g., role playing game) instead of the above-described video as the specific title, there is a request from a content provider that the game is to be started from an end of a chapter of the game, not from an interrupted position in a case where the game is resumed after returning to the menu screen. However, this request cannot be satisfied with the current DVD video specifications.
(B) There is a portion difficult to use concerning language setting for display.
(B1) A menu description language code cannot be changed with a command which can be designated in the content, and the authoring is complicated.
In the current DVD video specifications, the menu description language code M_LCD is set into SPRM(0) (0-th system parameter: 16 bits) of navigation data, and the value is stored in the memory of the information reproduction device. In the current DVD video specifications, a command for changing the value of SPRM(0) does not exist in a command list which can be set in the content, and it is possible to change the value of SPRM(0) only by user designation under a special condition. Specifically, the value of SPRM(0) can be changed using a user operation function called Menu_Language_Select ( ) in user functions arranged in the information reproduction device, but there is a restriction that the user operation called Menu_Language_Select ( ) can be set only during the stopping of the operation of the information reproduction device. A screen for exclusive use is displayed to set the user operation using a remote controller.
The value of SPRM(0) cannot be changed with the command which can be set in the content in this manner. Therefore, a screen for selecting the menu description language code needs to be prepared with respect to a plurality of menu description language codes in the content (especially VOB data on menu information) so that any setting of the value of SPRM(0) can be handled. The authoring operation at the time of preparation of the content has been very difficult.
(B2) There is a danger that menu description language code information set by the user is deleted.
For example, supposing that a command capable of changing the value of SPRM(0) is newly added in order to solve problem (B1). Then, even when the user carefully sets a specific menu description language code (e.g., set Japanese to SPRM(0)), there is a danger that the value of SPRM(0) is automatically changed by the presentation of the content. When the menu description language code is automatically changed by the command, the user feels dissatisfied. Additionally, a necessity to set the menu description language code again by the user is generated, and this causes a problem that burdens on the user increase.
[2] There is a problem where a content representing power for the user is lacking.
(C) Disadvantage concerning seamless play with respect to a still picture
(C1) A seamless play between a moving picture and still picture is not possible with the current DVD video content.
The current DVD video assures the seamless play of the moving picture (Movie Content), and connection/play is seamlessly possible between different VOBs (or different titles) (without interrupting the screen of the moving picture halfway). On the other hand, for example, when the still picture displayed in a slide show (one display method with respect to the still picture, in which the displayed still picture is automatically switched) is switched to the moving picture, the seamless play is not assured, and video or audio stands still halfway depending on the information reproduction device in some case. Reasons why the seamless connection is not assured at a time of the switching to the moving picture from the still picture with the current DVD video content are as follows.
i) In an extended system target decoder (E-STD) in which the seamless play is assured, an access unit is defined in a moving picture object, and the values of a system time clock (STC: a clock value forming a reference) set to a separation unit, video decoder unit, sub-picture decoder unit, and audio decoder unit are switched in a boundary position of the access unit. On the other hand, the access unit cannot be defined with respect to the still picture in the current DVD.
That is, a picture continues to be output constantly continuously by a field unit of the moving picture, whereas the picture is only intermittently output in the still picture displayed, for example, in the slide show. In a data structure in a still picture object, a sequence end code (sequence_end_code) is arranged immediately after an I picture (intra picture) constituting a still picture in accordance with specifications of moving picture experts group 2 (MPEG-2). In the video decoder unit, when this sequence end code is detected, the decoding is stopped until the next I picture is input. Therefore, in the conventional DVD video, the access unit such as the moving picture cannot be set in a timing period in which the still picture is intermittently output.
ii) Switching between common parities has been permitted as a switching timing between the still pictures in the conventional DVD video. That is, after the previous still picture ends in a top field (or a bottom field), the next still picture is permitted to be started from the top field (or the bottom field). Therefore, when the still picture is switched to the moving picture halfway in a frame, the seamless connection is not performed, and there is a danger that the screen is disturbed at a switching end.
(C2) Multi-angle play in which the still pictures are combined or multi-angle play between the moving picture and still picture cannot be performed.
In the current DVD video, it is difficult to perform the multi-angle play in which slide shows of still pictures (still picture content) are combined or the multi-angle play in which the slide show of the still pictures is combined with the moving picture. When multi-angle play handling content is forcibly prepared, the seamless play is not assured with respect to the still picture. Therefore, multi-angled still pictures cannot be continuously played back (the still picture is stopped halfway without being continuously switched), or the screen stops halfway without being smoothly switched at the switching end between a screen of multi-scene and that of one sequential scene. In the moving picture, an interleaved unit (ILVU) is defined in which scattered arrangement is performed for each angle in an interleaved block, whereas the definition of the ILVU with respect to the still picture is not clarified in the current DVD video. A period until the switching of the screen is long in the still picture (the same still picture continues to be played back for a long time), and therefore there has not been a mechanism capable of displaying the corresponding still picture immediately after angle switching at present. Furthermore, as described in (C1), on detecting the sequence end code arranged immediately after the I picture corresponding to the still picture, a decode process of the video decoder unit is temporarily stopped until the next I picture comes. Therefore, the arrangement of the sequence end code is inhibited in video data in a cell constituting the interleaved block in the current DVD video specifications.
(D) The seamless play is not assured in VOB where the command by a cell unit is included.
In the DVD video of the current standard definition (SD), it is possible to designate the command by the cell unit in a program chain (PGC). This command information is recorded in a cell command region in program chain information (PGCI) which is a region where management information of the PGC is recorded. The cell command is executed at the time of the ending of the presentation of the cell in which this cell command is set. Therefore, the presentation of the next cell can be temporarily interrupted. Therefore, the seamless play between the cells is not assured at the presentation time of VOB including the cell command in the current SD DVD video.
(E) Disadvantage on Highlight Information
(E1) There is a deviation of a display period (set period) between highlight information and sub-picture.
A menu of the highlight information is displayed at the presentation time of a video title image, and content can be prepared in such a manner that the user can perform an interactive operation. In this case, it is necessary to switch the highlight information or to change the content of the highlight information in accordance with the content of the video title image being played back, and therefore precision of a display period or executable period of the highlight information is important. In the DVD video content of the conventional SD, a button displayed in the screen includes a combination of two types of different streams of a sub-picture stream presenting the image of the button and a video stream including the highlight information required for executing the command designated by the button.
The effective executable period of the highlight information is determined by time information of start and end (PTM: presentation time), and completely coincides with a display period of the sub-picture for use mainly in subtitles. There is a problem that menu selection ends, when the sub-picture ends. Therefore, when a content producer is to prepare the content of the subtitles simultaneously combined with the menu, there are restrictions as to the preparation of the content. For example, the user has to select the menu within an effective (display) period of the sub-picture. The content producer cannot prepare the content as imaged, a degree of freedom is limited, and the content supplied to the user is forced to be limited.
(E2) A selection item image of the menu is not multicolored.
Since only a combination of 16 colors can be represented in the current SD DVD video content, a degree of appeal to the user is low, and multicolored presentation cannot be performed.
(E3) A designated region of the highlight information cannot be set to a shape other than a rectangular shape.
The shape other than the rectangular shape cannot be set as the designated region of the highlight information in the DVD video content of the current SD, and it has not been possible to prepare the content having varieties of highlight information such as a triangular shape and a star shape.
(E4) The same button cannot be set with respect to a plurality of regions distant from one another on the screen.
The same button can be set only in an integrated region in the DVD video content of the current SD.
On the other hand, it is easy to link the same URL to a plurality of regions in the screen of PC or a homepage screen of internet, and the current SD DVD video content has been inferior to the PC screen or the homepage screen of internet.
(F) There is a problem that a background music discontinues at the switching time of the menu screen.
In the current SD DVD video content, audio information (background music) at a menu screen display time accompanies to each menu. Therefore, every time the menu screen changes, the audio information accordingly changes.
The existing SD-DVD video content cannot satisfy a content provider's demand that a background sound be played back continuously without any interruption, even when the menu is changed.
(G) A sub-picture stream corresponding to a clear picture screen having a high resolution cannot be recorded.
In the existing DVD video specifications, the only standard definition (SD) picture having a resolution of 480 lines×720 pixels at maximum is supported, for example, in National Television System Committee (NTSC). An upper limit value of a size of the sub-picture unit SPU for use in subtitles or the like is set to 53,220 bytes or less in consideration of the upper-limit resolution. Therefore, when a high definition (HD) picture having a high resolution, for example, of 1,080 lines×1,920 pixels is handled as the picture information in the NTSC, and the corresponding sub-picture unit (SPU) having the high resolution is to be recorded, a problem occurs that the unit cannot enter the existing sub-picture unit (SPU) whose upper limit is defined as 53,220 bytes. To solve the problem, when the upper limit value of the size of the sub-picture unit (SPU) is simply enlarged, a necessity for the change of the data structure in the sub-picture unit (SPU) is generated, and the compatibility with the processing circuit or the reproduction control program for use in the conventional DVD player cannot be easily taken. Therefore, a problem occurs that the player which handles even the HD picture becomes expensive. A content producer also demands reuse of the conventional content, and there has been a demand for diversion of content assets of the conventional sub-picture unit (SPU) with respect to the contents for HD in addition to the sub-picture unit (SPU) for HD pictures.